The invention relates to a ball-and-socket joint connection and, in particular, is for a holding arm system for holding surgical instruments, with a joint ball sitting in a seat of a joint casing and permitting rotations in several axes and with a ball-shaped joint socket which can be axially displaced to and from the joint ball in a cylindrical section of the joint casing, as well as to a holding arm segment using this joint connection.
Within the framework of ergonomic analyses of the operating system xe2x80x9cOperating theater for minimal-invasive surgeryxe2x80x9d in particular with the assisting operator, there has been shown to be a large quantity of burdening static holding work. This results primarily from the absence or the deficient design of suitable auxiliary devices for performing the static hand work. For example, endoscope optics equipped with video cameras are guided by the assistant directed by the operator and for a large period of time during the duration of the operation are held as still as possible. The on-set of fatigue from holding the endoscope optics lead to an inadvertent wandering and to the shaking of the endoscope picture. Similarly this also applies to the holding of organ parts with the help of forceps or wound hooks which with lengthy static holding work with holding forces of more than 15% of the muscle force act in a tiring and ability-reducing manner. Useful holding arm systems which are equipped with suitably designed joint connections may be a solution to this problem.
DE 295 21 305 shows the above mentioned ball-and-socket joint connection for fixing the joint ball in a joint casing using a pressing plate which is actuated by a magneto-restrictive actuator element. If an electrical voltage is applied to the magneto-restrictive element of the actuator this extends and presses, by way of the pressing plate, the joint ball against a conical seat formed in the joint casing. Accordingly, the friction forces acting between the pressing plate, the joint ball and its seat and thus the moment which may be transmitted by the ball-and-socket joint are increased. In this manner an active fixing of the ball-and-socket joint connection may be achieved. In reverse the ball-and-socket joint connection is again released in that the voltage to the magneto-restrictive element of the actuator is switched off.
Although this ball-and-socket joint connection has fulfilled its objects within the framework of the mentioned applications in the operating theater, it has the disadvantage that the individual parts of the ball-and-socket joint connection are not separable from one another, which makes its cleaning and preparation more difficult. Furthermore, the known ball-and-socket joint connection is very complicated and thus comparatively expensive because of the type of actuators equipped with magneto-restrictive elements and because in each case electrical voltages must be applied to these actuators, wherein these voltages must individually be able to be switched on and off. It is therefore rarely applied to simple holding arm systems for holding, for example, forceps systems or wound hook systems
It is the object of the invention to provide a ball-and-socket joint connection which permits rotation in several axes, allows jerk-free movements, can be fixed and again released in a fine-touch manner by way of a simple operating mechanism and which may be completely separated in a simple manner.
A ball-and-socket joint connection achieving the above object according to an essential aspect of the invention has a magnet which produces a magnetic force between the joint ball and the joint socket such that they are drawn to one another. The ball-and-socket joint of the invention has an actuation element for displacing the joint socket, wherein the joint ball is fixable in the seat of the joint casing by way of retracting the joint socket and with this the joint ball by way of the magnet force is pressed into the seat of the joint casing, and the joint ball by displacing forwards the joint socket with the actuation element is separable from the seat.
In a preferred embodiment of the invention, a spring element exerts a pretensioning force on the joint socket in the direction of its retracted position, wherein the joint socket by way of actuation of the actuation element is displaceable against the pretensioning force of the spring element.
In this manner the ball-and-socket joint connection according to the invention may be released with one hand and the parts may either be changed in their position or separated from one another. In reverse, on account of the pretensioning force brought about by the spring element, the locking of the ball-and-socket joint connection also may be carried out with one hand.
In another preferred embodiment the seat of the joint casing is provided with a shallow cone so that the joint ball in the retracted position of the joint socket comes to lie on the cone surface of the seat. The more shallow the cone, the greater the normal force exerted by the ball surface onto the cone-shaped seat by way of the magnetic force. The holding force is also greater in dependence on the friction coefficients. With steel the cone angle is preferably less than 7xc2x0.
The fixing of the joint ball in its seat may also be achieved in that the joint ball is completely or partly elastically deformable. Due to the deformation forces transmitted by the magnet force from the joint socket and the seat to the joint ball, the ball is elastically deformed and is thus no longer movable in its seat.
A further solution to obtain a secure locking of the joint ball in its seat is to provide a uniform grid on the surface of the joint ball and a fitting counter pattern on the seat of the joint casing. For example, the grid of the joint ball is designed in the manner of a golf ball. Accordingly, the grid of the joint ball engages with a positive fit with the counter pattern on the seat of the joint casing in the locked position. The joint ball bears on the seat and is held securely in this position.
The magnetic force may either be produced in that the joint socket itself is formed as an electromagnet or permanent magnet or contains such. Alternatively, the joint ball is either formed as a permanent magnet or contains such or also an electromagnet.
Due to the open formation of the joint casing with the shallow cone, the joint ball in the released condition of the ball-and-socket joint connection may be simply removed from the joint casing.
In a holding arm system according to the invention on one end of a rod-shaped arm there is provided such a ball-and-socket joint connection according to the invention. Alternatively, each of both ends of a holding arm may be provided with such a ball-and-socket joint connection.
For the axial displacement of the joint socket to each individual ball-and-socket joint connection of such a holding arm segment there may be allocated a suitable actuation element.
In another embodiment, the actuation element is in the form of a curved bow which protrudes in the direction of the rod-shaped arm and is pivotably movable on an axial extension of the joint socket, this extension projecting through a bore in the base part of the joint casing. If on both ends of a rigid arm there is fixed a ball-and-socket joint connection according to the invention, the curved actuation bow itself may form the spring element in that it is elastically formed and in the tensioned condition is pivotingly movably applied between the two extensions, pointing to one another, of the joint sockets of the ball-and-socket joint connections on both ends of the holding arm.
The handling of a holding arm system consisting of any number of individual holding arm parts is relatively simple on account of the ball-and-socket joint connection according to the invention and a holding arm segment equipped with this since, for adjusting the respective holding arm segment, only the bow-shaped actuation element engaging on both ball-and-socket joint connections lying opposite one another on the holding arm need be actuated in that it is pressed towards the holding arm against the spring force.
Accordingly, the two joint sockets arranged piston-like in the joint casing are in each case displaced axially in the direction towards the joint ball, by which means these are equally pushed out of the seat of the joint casing by a certain distance. On account of this displacement, the friction between the seat and the joint ball is removed and allows for an easy adjustability of the holding arm.
If on the other hand the pressure force acting on the bow-shaped actuation element is reduced this on account of its elasticity returns to its initial position. Simultaneously the two joint sockets are pulled into the joint casing along with the joint balls. The renewed bearing of each joint ball on the conically formed seat on account of the high friction between the seat and the joint ball as well on account of the high magnet force has the effect that the respective holding arm parts are again brought into an unadjustable or difficultly adjustable position to one another.
The above discussed possible separation by way of the forward displacement of the joint socket against the pretensioning force of the spring element, apart from the advantage of the disassembling into smaller individual pieces and thus of an optimal cleaning and preparation, offers the possibility of combining individual elements, intermediate pieces, branching etc. with one another in any way.
The various features of novelty which characterize the invention are pointed out with particularity in the claims appended to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects obtained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.